Probing the magnetic phases in the Ni-V alloy close to the disordered ferromagnetic quantum critical point with muSR

TL;DR

This study uses muon spin relaxation to investigate magnetic inhomogeneities and phase transitions in Ni-V alloys near the ferromagnetic quantum critical point, revealing evolving local magnetic environments.

Contribution

It provides detailed muSR analysis of magnetic phases and inhomogeneities in Ni-V alloys close to the quantum critical point, highlighting changes in local magnetic fields with V substitution.

Findings

Homogeneous ferromagnetism in pure Ni confirmed by single precession frequency.

Magnetic inhomogeneities increase with V substitution, evidenced by damped oscillations.

Near the critical concentration, complex relaxation behavior indicates evolving magnetic dynamics.

Abstract

Zero (ZF) and longitudinal field (LF) muon spin relaxation data of the {\it d}-metal alloy Ni$_{1-x}$V$_{x}$ are presented at several vanadium concentrations $x$ below and above the critical $x_c \approx 11$% where long-range ferromagnetic (FM) order is suppressed. The clear single precession frequency observed for Ni, as expected for a homogeneous FM, changes to rather damped oscillation with small V substitution at $x=4$%, confirming magnetic inhomogeneities caused by the less magnetic V environments in the magnetic Ni matrix. Furthermore, local fields and spatial field distributions can be estimated to characterize different inhomogeneous regimes developing with $x$ in the FM phase of Ni$_{1-x}$V$_{x}$. In the regime of $x=7-10$% a Kubo Toyabe function well describes the low temperature ZF and LF asymmetry data supporting a static Gaussian field distribution. Closer to the quantum critical concentration a single scale static Kubo Toyabe function with one field distribution is not sufficient to describe the muon relaxation. These data indicate that further changes in spatial distributions and dynamics are evolving as expected within the critical regime of a disordered quantum critical point.